This invention relates to new flexible polyurea foam articles in the density range of from 200 to 600 kg/m.sup.3 and a process for the production thereof.
The production of flexible polyurethane foam articles having a compact skin zone and an integral density distribution by foaming reaction mixtures based on organic polyisocyanates, polyether and/or polyester polyols and low molecular weight polyols as chain lengthening agents inside molds is known (see e.g. Becker/Braun, Kunststoff-Handbuch 7, Polyurethane, Publishers Dr. G. Oertel, Carl Hanser Verlag, Munich, 1983). The production of microcellular molded parts having densities above 800 kg/m.sup.3 using certain aromatic diamines as chain lengthening agents (DE-AS No. 2,622,951) and/or using relatively high molecular weight compounds containing isocyanate reactive groups at least 50% of which are primary or secondary amino groups (EP-A Nos. 0,081,701, 0,093,861, 0,093,862 or DE-OS No. 3,215,909) is also known. The number of urea segments in the synthetic materials is increased by the use of amine starting components. The mechanical properties of the polyisocyanate polyaddition products can thus be improved. The production of molded parts on the basis of such urea-modified polyurethanes or of pure polyureas has, however, been restricted to the production of high density products with densities above 800 kg/m.sup.3. This may be attributed to the fact that the reaction between the isocyanate groups and amino groups generally proceeds extremely rapidly so that the reaction which results in cross-linking is substantially completed before any foaming agents present can act. Therefore, all of the specific examples of molded parts described in the above-mentioned prior publications have densities above 800 kg/m.sup.3. Although the production of cellular molded parts having a preferred density range of from 0.25 to 0.7 g/cm.sup.3 is mentioned in the general description in DE-OS Nos. 3,215,907 and 3,215,909, the possibility of producing such foams from the aminopolyethers with aliphatically bound amino groups disclosed in these prior publications has not been documented.